Learn on PengienVision, Mathematics, Grade 5Chapter 8: Apply Understanding of Multiplication to Multiply Fractions

Lesson 8: Multiplication as Scaling

In this Grade 5 lesson from enVision Mathematics Chapter 8, students learn to use multiplication as scaling to predict whether a product will be greater than, less than, or equal to a given number without calculating. Students discover that multiplying by a fraction less than 1 shrinks a value, multiplying by a fraction greater than 1 increases it, and multiplying by a fraction equal to 1 leaves it unchanged. Practice includes comparing products using inequality symbols and ordering expressions by size using number sense rather than computation.

Section 1

Predicting Product Size Using a Scaling Factor

Property

When a number aa is multiplied by a fractional scaling factor ff:

  • If f<1f < 1, the product is smaller than aa. (a×f<aa \times f < a)
  • If f=1f = 1, the product is equal to aa. (a×f=aa \times f = a)
  • If f>1f > 1, the product is larger than aa. (a×f>aa \times f > a)

Examples

Section 2

Comparing Scaled Products

Property

To compare two products with a common factor, a×ba \times b and a×ca \times c (where a>0a > 0), you only need to compare the scaling factors, bb and cc.
The relationship between the products will be the same as the relationship between the scaling factors.

If b>cb > c, then a×b>a×ca \times b > a \times c.

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Chapter 8: Apply Understanding of Multiplication to Multiply Fractions

  1. Lesson 1

    Lesson 1: Multiply a Fraction by a Whole Number

  2. Lesson 2

    Lesson 2: Multiply a Whole Number by a Fraction

  3. Lesson 3

    Lesson 3: Multiply Fractions and Whole Numbers

  4. Lesson 4

    Lesson 4: Use Models to Multiply Two Fractions

  5. Lesson 5

    Lesson 5: Multiply Two Fractions

  6. Lesson 6

    Lesson 6: Area of a Rectangle

  7. Lesson 7

    Lesson 7: Multiply Mixed Numbers

  8. Lesson 8Current

    Lesson 8: Multiplication as Scaling

Lesson overview

Expand to review the lesson summary and core properties.

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Section 1

Predicting Product Size Using a Scaling Factor

Property

When a number aa is multiplied by a fractional scaling factor ff:

  • If f<1f < 1, the product is smaller than aa. (a×f<aa \times f < a)
  • If f=1f = 1, the product is equal to aa. (a×f=aa \times f = a)
  • If f>1f > 1, the product is larger than aa. (a×f>aa \times f > a)

Examples

Section 2

Comparing Scaled Products

Property

To compare two products with a common factor, a×ba \times b and a×ca \times c (where a>0a > 0), you only need to compare the scaling factors, bb and cc.
The relationship between the products will be the same as the relationship between the scaling factors.

If b>cb > c, then a×b>a×ca \times b > a \times c.

Book overview

Jump across lessons in the current chapter without opening the full course modal.

Continue this chapter

Chapter 8: Apply Understanding of Multiplication to Multiply Fractions

  1. Lesson 1

    Lesson 1: Multiply a Fraction by a Whole Number

  2. Lesson 2

    Lesson 2: Multiply a Whole Number by a Fraction

  3. Lesson 3

    Lesson 3: Multiply Fractions and Whole Numbers

  4. Lesson 4

    Lesson 4: Use Models to Multiply Two Fractions

  5. Lesson 5

    Lesson 5: Multiply Two Fractions

  6. Lesson 6

    Lesson 6: Area of a Rectangle

  7. Lesson 7

    Lesson 7: Multiply Mixed Numbers

  8. Lesson 8Current

    Lesson 8: Multiplication as Scaling